1. Field of the invention
The present invention relates to a beam monitor for a high-output laser, and in particular to a beam monitor for a high-output laser which detects a high-output laser beam intensity while detecting the beam characteristics of the mode pattern.
2. Description of the Prior Art
In a high-output laser device used, for example, in a laser process machine, adjustments are made to give the maximum output and to output a beam with an optimum mode pattern for speed and accuracy in processing.
However, in this type of high-output laser transmitter, once the adjustment is made, the alignment of the optical system gradually deteriorates over a period of time for a variety of reasons. As a result, the system must be realigned every few weeks.
Also, when maintenance is being carried out, slight readjustments are necessary after the lenses and mirrors are replaced. This is usually because the centerline of the curve of the mirror does not necessarily coincide with the centerline of the optical system.
As a result, the optical system must be realigned quite frequently.
However, if the optical system of the laser transmitter is an ideal resonance system, there is a comparatively simple relationship between the output power and the adjustment angle of the mirror. This relationship is shown in FIGS. 1 (a), (b), (c), (d), (e), and (f). As can be seen from these diagrams, the mirror adjustment angle .theta. corresponding to the maximum output, the mirror adjustment angle .theta. corresponding to the optimum mode pattern (specifically, the single mode of FIG. 1 (e)) are in agreement. Accordingly, in order to obtain the optimum mirror adjustment angle .theta., if, for example, only the output power is monitored, it may be adjusted to give a maximum.
However, the optical system of an actual laser device used in equipment such as a laser processing machine is not usually an ideal resonance system. Therefore, when aligning this type of optical system for a laser device, the output power and the mode pattern are monitored independently, and the optical system must be adjusted so that the output power is at its optimum.
For this reason, in conventional devices, an output power detection sensor is provided on the rear of, for example, the rear mirror, and the beam is directed onto, for example, an acrylic plate, so that a burn pattern is obtained on this acrylic plate. Then, the optical system is aligned based on the values of the output detected by this output sensor and the burn pattern on the acrylic plate.
However, with this type of method, the burn pattern must be reobtained for the degree of adjustment of the optical system, so that the adjustment operation becomes very time-consuming and a high degree of skill is required to perform it.
In addition, the operation of directing the laser beam onto the acrylic plate is extremely dangerous because it is necessary to perform this operation while a high output beam is emitted.